1. Field of the Invention
The present invention relates generally to a technical field of an inkjet recording system utilized for a variety of printers, and more particularly to an inkjet recording head that actualizes an ink ejection in a direction oblique to an ejection surface without any declines of productivity and workability and to an inkjet printer utilizing this inkjet recording head.
2. Description of the Related Art
A thermal inkjet recording system in which part of ink is quickly vaporized by heating with a heater and ink droplets are ejected from a nozzle by a force of expansion thereof onto a recording medium for recording has hitherto been utilized for a variety of printers (refer to JP 48-9622 A and JP 54-51837 A).
According to such a thermal inkjet recording system (which will hereinafter be simply called the inkjet system), nozzles from which ink (ink droplets) is ejected are normally bored in a plate member called an orifice plate or a nozzle plate, and the ink is ejected from the nozzles in a direction orthogonal to an ink ejection surface (a plate surface).
On the other hand, a scheme in which ink is ejected obliquely to the ejection surface (which will hereinafter be referred to as an “oblique ejection” or the like), is considered in the expectation that a variety of effects might be yielded.
What is known as a recording head in which a line head containing an array of nozzles extending in excess of one side of a sheet of image receiving paper can be manufactured at a low cost but with a high yield, is, for instance, an inkjet recording head (which will hereinafter simply be referred to as a recording head) that is elongated by arranging a plurality of small-sized recording heads (which will hereinafter simply called short heads) in a nozzle array direction.
Even in this type of recording head configured by arranging those short heads, it is required that a uniform and proper nozzle pitch be kept over an entire area of the nozzle array in order to record a high-quality image. An interval between the outermost nozzle of a short head and the edge of the short head in the nozzle array direction of the short head is, however, normally larger than the nozzle pitch Accordingly, if the short heads are arranged simply by abutting the edges on each other, it follows that the nozzle pitch increases at the joining portion between the respective short heads.
What is disclosed as a scheme for obviating this problem in JP 7-171956 A, is a recording head elongated by arraying a plurality of short heads, in which the nozzles of the respective short heads are inclined by 5° to 10° with respect to the ejection surface in the nozzle array direction, thereby ejecting the ink obliquely.
This recording head is capable of correcting an error in the nozzle pitch at the joining portion between the short heads in an ink impinging position (on the image receiving paper) by obliquely ejecting ink, i.e., capable of recording an image with a predetermined recording density over the entire area in the nozzle array direction of the recording head.
Further, streaky unevenness and spots are factors that may cause the decline of the image quality in the inkjet printer.
To obviate this problem, JP 2001-105584 A discloses an inkjet printer (inkjet recording apparatus) constructed to prevent occurrences of streaks and spots by disposing a plurality of heaters for a single nozzle and driving the respective heaters individually thereby changing at random directions in which ink is ejected from the respective nozzles during image recording.
Moreover, clogging in the nozzle of the recording head and the decline of the image quality due to contamination around the nozzle, are known as troubles in the inkjet printer. One factor that may cause these troubles is that some quantity of ink ejected from the nozzle and impinging upon the image receiving paper is splashed back from the image receiving paper, then adhered to the peripheral portion of the nozzle and dried.
What is known as a scheme for preventing this inconvenience is a method of preventing the contamination around the nozzle by obliquely ejecting ink in the direction orthogonal to the nozzle array and thus allowing the ink splashed back from the image receiving paper to flow in a direction spaced away from the nozzle.
Thus, the oblique ejection of ink in the inkjet system has many merits. While on the other hand, this oblique ejection is more disadvantageous in terms of a productivity of the recording head and so forth than in the normal recording head.
For example, boring the orifice plate obliquely (to the plate surface) to form the nozzle involves by far more laborious operations than forming the hole orthogonally to the plate surface and is disadvantageous in terms of the productivity, a production cost and a yield of the recording head.
Further, the inkjet printer disclosed in JP 2001-105584 A must have a plurality of heaters for one nozzle and is therefore still disadvantageous in terms of the productivity and the production cost of the recording head. This inkjet printer has also a low degree of freedom in the present situation where the hyperfine structure of the recording head is accelerated with a higher resolution. Moreover, the plurality of heaters are driven at random, and therefore the recording control becomes complicated.